B-staged polyurethane-isocyanurates from alkylene oxide condensate of novolak resins

ABSTRACT

1. A NORMALLY SOLID, FUSIBLE COMPOSITION CAPABLE OF BEING TRANSFORMED INTO A THERMOSET COMPOSITON BY SUBJECTING SAID FUSIBLE COMPOSITION TO HEAT, WHEREIN SAID FUSIBLE COMPOSITION COMPRISES THE REACTION PRODUCT OF (A) AN ALKYLENE OXIDE CONDENSATE OF A NOVOLAK, (B) A STOICHIOMETRIC EXCESS OF AN ORGANIC POLYISOCYANATE, AND (C) A CATALYTICALLY EFFECTIVE QUANTITY OF A CATALYST FOR PROMOTING THE FORMATION OF ISOCYANURATE FROM ISOCYANATE, WHEREIN THE REACTION IS INTERRUPTED BY COOLING BEFORE REACHING THERMOSET STAGE.

United States Patent 3,842,036 B-STAGED POLYURETHANE-ISOCYANURATES FROMALKYLENE OXIDE CONDENSATE OF NOVOLAK RESlNS Sui-Wu Chow, Somerville, andMarkus Matzner, Edison, N..l., assignors to Union Carbide Corporation,New York, N.Y.

No Drawing. Continuation-impart of application Ser. No. 238,588, Mar.27, 1972, now Patent No. 3,723,367. This application Jan. 31, 1973, Ser.No. 328,369

Int. Cl. C08g 22/14, 33/02 US. Cl. 260-47 CB Claims ABSTRACT OF THEDISCLOSURE 'Polyurethane-isocyanurates are produced from an alkyleneoxide condensate of a novolak resin, an organic polyisocyanate, and acatalyst that promotes the formation of isocyanurates from isocyanates.

This application is a continuation-in-part of our application Ser. No.238,588, filed Mar. 27, 1972, for Alkali Metal Mercaptides asUrethane-Isocyanurate Catalysts, now U.S. Pat. No. 3,723,367.

The invention relates to polyurethane-isocyanurates that are producedfrom an alkylene oxide condensate of a novolak resin, an organicpolyisocyanate, and a catalyst that promotes the formation ofisocyanurates from isocyanates, and to processes for the production ofsaid polyurethane-isocyanurates.

Polyurethanes have been produced by reacting essentially stoichiometricequivalents of an alkylene oxide condensate of a novolak with an organicpolyisocyanate. For instance, see British Patent No. 1,029,033. Morerecently, it has been disclosed that polyurethane-isocyanurates can beproduced by reacting a polyol with a significant stoichiometric excessof an organic polyisocyanate in the presence of a catalyst that promotesthe formation of isocyanurate from isocyanate. Such compositions aredisclosed, for instance, in US. Pat. No. 3,697,485. Among the polyolsthat have been disclosed as being useful in producingpolyurethane-isocyanurates are alkylene oxide condensates of bisphenol A(in German Pat. No. 2,014,899).

The present invention is based upon the discovery that usefulelastomeric to rigid thermoset compositions containing both urethane andisocyanurate groups can be produced from alkylene oxide condensates ofnovolak resins and organic polyisocyanates. The thermoset compositionsof the invention are more thermally stable than polyurethanes producedfrom comparable alkylene oxide condensates of novolaks. (By comparable,is meant a condensate that is derived from the same novolak and whichhas the same average polyether chain length.) Also, the thermosetcompositions of the invention have a higher cross-linking density and,hence, are more rigid at elevated temperatures than the aforesaidcompositions produced from bisphenol A-alkylene oxide condensates havingthe same polyether chain length. Therefore, the compositions of thisinvention develop green strength more rapidly than do the productsderived from bisphenol A, with attendant fabrication economies.

Broadly, the thermoset compositions of the invention are produced byreacting an alkylene oxide condensate of a novolak resin with astoichiometric excess of an organic polyisocyanate to form a urethanepolymer, and either subsequent to or simultaneously with the productionof said urethane polymer, some of the isocyanato groups of said organicpolyisocyanate are reacted to form isocyanurate groups.

p ICC In one aspect, the invention provides a one-stage process whichcan be carried out as a one-step reaction wherein all the reactants andcatalyst are reacted in one step to produce the thermoset composition.Alternatively, the one-stage process can be carried out as a two-stepreaction wherein all or part of the reactants are prereacted to form anisocyanato-terminated prepolymer, which is then contacted with thecatalyst and any remaining reactants to form the thermoset compositionsof the reaction.

In another aspect, the invention provides a two-stage process. Thetwo-stage process can be carried out by simultaneously reacting all thereactants and catalyst, but, wherein the reaction is interrupted beforea thermoset composition is produced. Instead, this first reactionproduces a normally solid (i.e., solid at room temperature), fusiblecomposition (such as is often referred to as a B-stage material) that iscapable of being transformed by the application of heat into a thermosetcomposition. Alternatively, the two-stage process can be carried out byfirst pre-reacting all or some of the reactants to produce a prepolymer,followed by contacting the prepolymer with the catalyst and anyremaining reactants to form an isocyanurate. Again, however, theisocyanurate production is interrupted prior to the production of athermoset composition, to produce a B-stage composition that cansubsequently be transformed into a thermoset composition by theapplication of heat.

The alkylene oxide condensates of the novolak resins that are employedin the invention are well known to those skilled in the art (e.g., seeBritish Pat. No. 1,029,033), as are the novolak resins per se. It isknown that the novolak resins are readily produced by the reaction of aphenol with, for example, formaldehyde. The phenol-formaldehyde resinsare known to exist as A- stage, B-stage and C-stage resins, with theC-stage resin being highly crosslinked and insoluble and infusible. Forthe purposes of this invention, the fusible A and B-stage novolak resinsare employed in the production of the alkylene oxide condensates. It isalso known that the novolak resins can be produced using substitutedphenols and that other aldehydes can be used instead of or in additionto formaldehyde. All of these are known, as are the methods by whichthey are produced, and for the purposes of this invention the termnovolak includes any of the 'known resins.

The reaction of the novolak resin with an alkylene oxide is readilycarried out in the presence of a suitable catalyst. This reaction iswell known and does not require extensive discussion herein to enableone skilled in the art to produce these compounds. Any of the alkyleneoxide compounds can be used in the production of these condensates. Thepreferred, however, are the aliphatic alkylene oxides containing up tofour carbon atoms. The most preferred are ethylene oxide, propyleneoxide, or mixtures thereof.

A particularly preferred condensate is the product formed by condensingpropylene oxide, ethylene oxide, or mixture thereof with the novolakproduced by the reaction of phenol with formaldehyde. Thisphenolformaldehyde novolak is a composition that contains the recurringunit that can be represented by the structural formula wherein at is asdefined above with respect to Formula I, wherein R can be hydrogen ormethyl, and wherein n is a number having an average value of at least 1,and up to about or more. Preferably, n represents a number having anaverage value of from at least 1 to about 12.

The alkylene oxide condensates of novolak resins are reacted with anorganic polyisocyanate. Any of the known organic polyisocyanates can beused. Illustrative thereof are the alkylene diisocyanates, such astetramethylene diisocyanate, pentamethylene diisocyanate, andhexamethylene diisocyanate; cycloalkylene diisocyanates, such ascyclohexylene-1,3-diisocyanate, and cyclohexylene-1,4- diisocyanate;aromatic diisocyanates, such as m-phenylene diisocyanate, p-phenylenediisocyanate, polymethylene polyphenylisocyanate (i.e., the productproduced by phosgenation of an anilineformaldehyde condensationproduct), 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate,naphthalene-1-4-diisocyanate, diphenylene-4, 4 diisocyanate, bis (4isocyanatophenyl) methane (MDI), bis(3-methyl-4-isocyanatophenyl)methaneand 4,4'-diphenylpropane diisocyanate; aliphatic-aromatic diisocyanates,such as xylylene-l,4-diisocyanate and xylylene-1,3-diisocyanate, thepolyisocyanates as disclosed in US. Pat. No. 2,683,730, as well as thepolyisocyanates listed in the publication of Siefken, Annalen, 562,pages 122-135 (1949). Also included are 4,4'-tris (isocyanatophenyl)methane, 3,10 diisocyanatotricyclo [5.2.1.0 decane,bis(2-isocyanatoethyl) carbonate, and bis(2isocyanatoethyl) fumarate.Preferred organic polyisocyanates include the aromatic polyisocyanatessuch as tolylene diisocyanate, MDI, and polymethylenepolyphenylisocyanate.

Organic polyisocyanates that have been prereacted with a stoichiometricdeficiency of an active hydrogencontaining compound can also beemployed.

The organic polyisocyanate is employed in the inven tion in an amount inexcess of that required to react with all of the reactivehydrogen-containing compositions present in the reaction mixture. Suchreactive hydrogencontaining compositions include the alkylene oxidecondensates of novolak resins described hereinabove, one or moreadditional polyols which may be employed if desired, and reactiveblowing agents such as water, which can be employed if a foam isdesired. To illustrate the proportions that are employed, normally theorganic polyisocyanate will be employed in amounts such that there areat least abount 1.2, and preferably from about 1.5 to about 5,equivalents of isocyanato group per equivalent of reactive hydrogen.

The thermoset compositions of the invention can be prepared by (1)pre-reacting all or part of the alkylene oxide condensate of a novolakwith the organic polyisocyanate to form a prepolymer, followed bycontacting this prepolymer with a catalyst that promotes the formationof isocyanurate from isocyanate, or (2) a one-step reaction in which thecondensate and polyisocyanate are reacted in a reaction mixture thatalso contains the catalyst. Because the said condensates are often veryviscous, it may be desirable in some cases to employ a diluent in thereaction mixture, especially when a prepolymer is being formed prior tocontacting with the catalyst. Such diluent can be a non-reactive diluentsuch as a non-reactive blowing agent (e.g., a fluorocarbon such asfluorotrichloromethane) or a solvent such as methylene chloride, or areactive diluent such as a low viscosity polyol. Illustrative lowviscosity polyols include polypropylene glycol having a molecular weightof about 2000 and poly(epsilon-caprolactone) having a molecular weightof about 530.

Among the catalysts that can be employed to promote the formation ofisocyanurate from isocyanate are the alkali metal mercaptides, which aredisclosed in applicants copending application Ser. No. 238,588, thedisclosure of which is incorporated herein by reference. he alkali metalmercaptides can contain a single mercaptide group in the molecule, orthey can have larger numbers thereof. The mercaptide can be aliphatic,aromatic, heterocyclic, cycloaliphatic or polymeric in nature. Thenature of the mercaptide compound is not the controlling factor; thepresence in the molecule of the AM group 15 the factor which impartscatalytic activity to the molecule. Thus, in the broadest sense thecatalysts can be defined by the formula:

III X(SM) wherein X is the organic moiety to which the SM group isattached, and n is a number having a positive value which can be as highas six, and even higher in polymeric substances. The organic moiety Xcan be an unsubstituted or substituted monovalent or polyvalent group.Thus, it can be a monovalent alkyl group of from 1 to 20 carbon atoms,or an alkenyl group of from 2 to 20 carbon atoms, or an aryl or alkarylor aralkyl group of from 6 to 10 carbon atoms, or a cycloalkyl orcycloalkenyl group of from 5 to 6 carbon atoms, or a heterocyclrc groupcontaining ring carbon atoms and nitrogen or sulfur or oxygen ring atomswhich ring can have 5 or 6 members; or, it can be a polyvalent radicalof any of said groups when there are two or more -SM groups attached tothe X moiety. It can also be a polymer chain to which the -SM groups areattached.

Illustrative of suitable alkali metal mercaptides are sodiumn-butylmercaptide, lithium sec-butylmercaptide, sodium hexylmercaptide,lithium decylmercaptide, lithium dodecylmercaptide, sodium2-hydroxethylmercaptide, sodium l4-hydroxytetradecylmercaptide, sodiumcarboxymethylmercaptide, lithium 2-carboxyethylmercaptide, lithium9-carboxynonylmercaptide, lithium 4-hexenylmercaptide, sodiumphenylmercaptide, lithium phenylmercaptide, potassium phenylmercaptide,lithium l-naphthylmercaptide, sodium triphenylmethylmercaptide, sodium4-chlorophenylmercaptide, sodium tolylmercaptide, lithiumxylylmercaptide, sodium cyclohexylmercaptide, and1,3,4-thiadiazole-2,5-di(sodiomercaptide). Also suitable are the alkalimetal salts of Z-mercaptobenzothiazole, octane dithiol, and the reactionproduct of sodium sulfide with oligomers of epichlorohydrin as well aspoly(alphamercaptomethyl ethylene oxide).

Any alkali metal mercaptide having at least one mercaptide group in themolecule can be used, including the monomercaptides and polymercaptides,provided that there are no substituents in the molecule that will undulyinterfere with the reaction of the isocyanato group and formation of theisocyanurate group. The mercaptides are characterized by the presence inthe molecule of at least one mercaptide group of the formula -SM,wherein M is an alkali metal atom such as lithium, sodium or potassium.The simplest mercaptides are those containing only one such group.However, the compounds suitable for use can contain as many as six ormore mercapto or mercaptide groups in the molecule. There can also bepresent in the mercaptide molecule other substituent groups, such ascarboxyl, hydroxyl, halogen, ester linkages, ether linkages, amidolinkages, or amp other group which would not exert a deterring effect onthe The alkali metal mercaptide catalyst is used at a concentration offrom about 0.01 to about mole percent, and preferably from about 0.5 to5 mole percent, the percentage being based upon total equivalents ofisocyanate employed in the process. Any catalytic amount sufiicient tocatalyze the reaction can be employed.

A solvent for the catalyst can be used and for this purpose a suitableorganic solvent can be employed. As examples of useful solventsdimethylformamide, dimethylsulfoxide, sulfolane, diethylene glycol,dioxane, and tetrahydrofuran are illustrative.

The alkali metal mercaptides are readily prepared by known methods, oneof which is the reaction of the alkali metal or the alkali metal hydridewith the organic mercaptan, preferably in solution. The said solutioncan be used directly in the process of the invention.

In addition to, or in place of, the abovedescribed alkali metalmercaptides, other catalysts can be employed to promote the formation ofisocyanurate from isocyanate. Such other catalysts include an organicorthoborate plus an alcoholate or phenolate as disclosed in US. Pat. No.3,697,485, and a strong base such as a tertiary amine plus an epoxide asdisclosed in US. Pat. No. 3,211,703.

The invention can be employed to produce solid elastomeric products,surface coatings, cast objects, molded objects, fiber-reinforcedobjects, or flexible, semi-flexible, semi-rigid or rigid foams. All ofthese types of product and their specific utilities are well knowncommercially, and those skilled in the art are familiar with thereactants and techniques necessary to produce a particular type ofproduct. Thus, it is known that flexible products are obtained in theabsence of highly functional crosslinkers or in the absence of largeamounts of polyols and polyisocyanates having functionalities greaterthan two. It is also known that as the functionality of the reactants isincreased the rigidity of the final product increases. In addition, itis known that the inclusion of a foaming agent will produce a foam whilethe exclusion of such agent will result in a solid nonfoamed product.

Along with the alkylene oxide condensates of novolak resins,conventional polyols can be employed in the invention. These are so wellknown in the art that they do not require a detailed and elaboratedescription herein. However, as illustrative thereof, one can mentionthe following types:

(a) Polyoxyalkylene polyols including the adducts of alkylene oxideswith, for example, water, ethylene glycol, propylene glycol, glycerol,1,2,6-hexanetriol, 1,1,l-trimethylolpropane, pentaerythritol, sorbitol,sucrose, alphamethylglucoside, alpha-hydroxyalkylglucoside, ammonia,triisopropanolamine, ethylenediamine, phosphoric acid, polyphosphoricacids such as tripolyphosphoric acid, and phenol-aniline-formaldehydeternary condensation products. The alkylene oxides employed in producingthe polyoxyalkylene polyols normally have from 2 to 4 carbon atoms.Propylene oxide and mixtures of propylene oxide with ethylene oxide arepreferred.

(b) Polyesters of polyhydric alcohols and polycarboxylic acids such asthose prepared by the reaction of an excess of ethylene glycol,propylene glycol, or glycerol, with phthalic acid or adipic acid.

(c) Lactone polyols prepared by reacting a lactone such asepsilon-caprolactone or a mixture of epsilon-caprolactone and analkylene oxide with a polyfunctional initiator such as a polyhydricalcohol, an amine, or an aminoalcohol.

(d) Phosphorus-containing derivatives such as tris(dipropylene glycol)phosphite and other phosphites.

(e) The polymer/polyols produced by the in situ polymerization of avinyl monomer in a polyol, as disclosed in U.S. 3,304,273, US. 3,383,351and US. 3,523,- 093.

The foregoing are merely illustrative and represent only a small numberof the many polyols known in the art that can be employed with thealkali metal mercaptide catalysts in the process of this invention.

The alkylene oxide condensate of a novolak resin, or mixture thereofwith one or more other polyols, that is employed in the invention canhave a hydroxyl number which can vary over a wide range. In general, thehydroxyl number of the polyol or polyol mixture employed can range fromabout 20, and lower, to about 1000, and higher, preferably from about 30to about 800, and more preferably, from about 35 to about 700. Thehydroxyl number is defined as the number of milligrams of potassiumhydroxide required for the complete neutralization of the hydrolysisproduct of the fully acetylated derivative prepared from 1 gram ofpolyol. The hydroxyl number can also be defined by the equation:

where OH=hydroxyl number of the polyol f=average functionality, that is,the average number of hydroxyl groups per molecule of polyolm.w.:average molecular weight of the polyol The exact polyol employeddepends upon the end-use of the polyurethane-isocyanurate product. Themolecular weight and the hydroxyl number are selected properly to resultin flexible, semi-flexible, or rigid products. The polyol or polyolmixture usually possesses a hydroxyl number of from about 200 to about1000 when employed in producing rigid products, from about 50 to about250 for semi-flexible products, and from about 20 to about 70 or morewhen employed to produce flexible products.

When a foam is desired, foaming can be accomplished by employing a minoramount (for example, from about 0.5 to 25 weight percent, based on totalweight of the reaction mixture), of a blowing agent which is vaporizedby the exotherm of the isocyanato-reactive hydrogen reaction. Preferredvaporizable blowing agents include halogen-substituted aliphatichydrocarbons which have boiling points between about 40 C. and 70 C.,and which vaporize at or below the temperature of the foaming mass, forexample, trichloromonofiuoromethane, dichlorodifluoromethane, andmethylene dichloride. Other useful blowing agents include water andlow-boiling hydrocarbons such as butane, pentane, hexane, cyclohexane,and the like. Other gases or compounds easily volatilized by theexotherm of the isocyanato-reactive hydrogen reaction can be employed. Afurther class of blowing agents includes the thermally unstablecompounds which liberate gases upon heating, such as N,N'-dimethyl N,Ndinitrosoterephthalamide.

In addition to the catalyst for promoting the production ofisocyanurate, one can also have present in the reaction mixture any ofthe known catalysts previously used in the production of polyurethanes.These can comprise, for example, from 0.05 to 1 weight percent or moreof the reaction mixture. Illustrative thereof are:

(a) tertiary amines such as N-methylmorpholine, N- ethylmorpholine,N,N,N',N' tetramethyl 1,3 butanediamine, 1,4 diazabicyclo[2.2.2]octaneand bis[2-(N,N dimethylamino) ethyl] ether;

(b) salts of organic acids with a variety of metals such as alkalimetals, alkaline earth metals, Al, Sn, Pb, Mn, Co, Ni, and Cu,including, for example, sodium acetate, potassium laurate, calciumhexanoate, stannous acetate, stannous octoate, stannous oleate, leadoctoate, and metallic driers such as manganese and cobalt naththenate,and;

(c) organometallic derivatives of tetravalent tin, trivalent andpentavalent As, Sb, and Bi, and metal carbonyls of iron and cobalt.

Small amounts, e.g., about 0.001% to 5.0% by weight, based on the totalreaction mixture, of an emulsifying agent can be employed when producingfoams. Examples include polysiloxane-polyoxyalkylene block copolymershaving from about 10 to percent by weight of siloxane polymer and fromto 20 percent by weight of alkylene 7 oxide polymer, such as the blockcopolymers described in U.S. Pats. 2,834,748 and 2,917,480. Anotheruseful class of emulsifiers is the group of non-hydrolyza-blepolysiloxane-polyoxyalkylene block copolymers. This class of compoundsdiifers from the above-mentioned poly- 8 about 6.57 wt. percent of OH,and toluene diisocyanate (TDI) (8.7 grams, 0.1 equivalent of NCO) weremixed at 100 C. When the mixture became homogeneous, catalystsconsisting of about 0.08 gram (0.6 mole percent with respect to NCO)each of benzyldimethylamine and phenyl siloxane-polyoxyalkylene blockcopolymers in that the glycidyl ether were added, and the mixture wasthen alpolysiloxane moiety is bonded to the polyoxyalkylene lowed tostand at 100 C. A hard solid was formed in moiety through directcarbon-to-silicon bonds, rather than ab ut ten minutes no flow wasreached n about eight through carbon-to-oxygen-to-silicon bonds. Thesecopolymlnutesl The reafitlbn Was quenched y lrpmefslng the mersgenerally contain from 5 to 95 Weight percent, and 10 vessel whichcontained the reaction mixture 1n a Dry Icepreferably from 5 to 50weight percent, of polysiloxane acetofle bath- The P y was then p f A 10polymer ith th remainder b i l lk l 20-m1l clear and transparent filmwas compression molded polymen at about 200 C. under a pressure of about100 p.s.i. for The examples set forth below illustrate certain aspects 1minute followed y a pf l of about 10,000 P- for of the invention. Allparts and percentages are by weight, 9 mlnutes- T film lefalned ltSshape on removal from 1. otherwise Stated the mold w1thout cooling. Thefilm was insoluble in sol- LE 1 vents such as a mixture of phenol andtetrachloroethane; EXAMP dimethylformamide; and halogenatedhydrocarbons. No Production of novolak-propylene oxide condensate fusionwas obtained on attempted remolding of the film. A solution of novolakresin in propylene oxide contain- Thesed observatons mdlcgte that the P9j ing about 2 weight percent catalyst (with respect to Vance, to a stage(t ermoset) 121305111911 durmg hovolak) is maintained at 10021206 undfirautoge molding. These films are tough and abrasion resistant maneouspressure for 24 hours Excess propylene oxide is terials, and can beemployed 1n ut1l1t1es requiring such removed by evaporation underreduced pressure. The re- P P sulting viscous condensate is washed withwater to remove 25 Pfeparatlons 0f tbermoset COIIIPOSIUOIIS 0f Varymgresidual catalyst, and is then dehydrated by azeotropic NCO/ OH ratiosand 0f novolak-pl'opylene OXide Condendistillation with toluene. Table1, below, sets forth some sates of different OH contents were carriedout in a similar typical experimental conditions and results. manner,that is, by the two-stage process described above.

TABLE 1 Novolak Propylene oxide Catalyst Condensate product Equiv. ofIdentifiphenolic Percent OH Run number cation OH Parts Moles Parts Iden.Parts 0 number s 318 12 696 DBMA 0.4 6. 57 22.6 2 212 12 696 NaOMe 1.44. 15.3 2 212 12 696 NaOMe 1.4 5. 02 16.5 2 212 12 696 NaOMe 1.4 4.8211.6

1 Novolak A was made from 63 parts of formaldehyde per 100 parts ofphenol. It had an average of 4 to 6 phenol moieties per molecule.Novolak 13-66 parts of formaldehyde per 100 parts of phenol. Average of6 to 8 phenol moieties per molecule. Novolak C67.5 parts of formaldehydeper 100 parts of phenol. Average 7 t0 9 phenol moieties per molecule.

I BDMA=Benzyldimethylamine; NaOMe= Sodium methoxide.

EXAMPLE 2 Production of B-stage polyurethane-isocyanurate thermosetcompositions Novolak-propylene oxide condensate No. 1 (from Example l)(5.5 grams, 0.024 equivalent of OH) containing The experiments aresummarized in Table II. The catalyst employed in each sample was amixture of phenyl gylcidyl TABLE II Polyisocyanurates fromnovolak-propylene oxide condensate and TDI atalyst mole Reaction No flowGrams of (NCO)/ Sample Condensate conden- DI, (OH) percent temp., timenumber designation sate grams moles of NCO C. mins A 2. 1 3. 25 3 0. 5100 11 A. 3. 1 2. l8 2 0. 8 100 1 A 12.4 6. 5 1. 5 1. 0 2-3 B 10. 9 5. 22 0. 8 70 2 D 10. 2 5. 2 2 1. 0 70 2 C 12. 9 7. 8 1. 5 0. 7 70 3 E 10. 95. 2 2 1. 0 70 1-2 F 9. 72 5. 2 2 1. 0 70 1-2 Nora:

novolak was prepared from 63 parts of formaldehyde per parts of phenol.:t was 5.7;

n was 2.

D=Novolakpropylene oxide condensate containing 5.02 weight per cent ofOH. The novolak was prepared from 66 parts of formaldehyde per 100 partsof phenol. x was 6.7;

n was 4.

E=Novolak-propylene oxide condensate containing 4.82 weight per cent ofOH. The novolairzvgas prepared from 67.5 parts of formaldehyde per 100parts of phenol. x was 7.4; n was F=Novolakpropylene oxide condensatecontaining 5.26 weight per cent of OH. The IZlgVOlBJI wz asmpreparedfrom 68.2 parts of formaldehyde per 100 parts of phenol. a: was

. n was Representative properties of the thermoset compositions whoseproduction is set forth in Table II are displayed below in Table III.Table III also displays the values for x and n from Formula II for eachcondensate, as well as the ratio of isocyanate to hydroxyl (NCO/OH) inthe reaction mixture.

TABLE III Pendu- Perlum 1m- Tensile Tenslle cent pact, NCO/ modulus,strength, elonga- Tcg, foot-lbsJ z n OH p.s.i. p.s.i. tion cubicinch 72. 4 3 280, 000 10, 000 5. 5 170 7. 3 7 2. 4 2 236.000 7, 800 4.0 124 7.7 .7 2.4 1.5 300,000 12,000 5.5 76 9 7 4. 5 2 275, 000 8, 300 4. 5 64 107 4 2 330, 000 7, 700 3.0 68 12 .7 2 1. 5 416, 000 9, 000 2. 5 106 6 .44. 25 2 205,000 3,500 2.0 80 6 5 .8 3. 75 2 Not fully cured Theforegoing Example 2 illustrates one way of carrying out the two-stageprocess of the invention. As a general rule, the slower catalysts, suchas the tertiary amineepoxy system illustrated in Example 2, arepreferred for the two-stage process. When using such catalysts, anelevated temperature of the order of 70 to 100 C. is employed toinitiate the reaction of isocyanate to form isocyanurate groups. Thereaction, once initiated, is exothermic, and additional heating is notrequired. To form a B-stage material, the reaction is quenched to a lowtemperature, e.g., below C. The B-stage material is then cured byheating to an elevated temperature of the order of 190 to 200 C. for aperiod of at least about minutes. Normally, pressure is required tocause the B-stage material to flow. Initially, a low pressure isdesirable, such as a pressure of 50 to 150 p.s.i. for about 1 minute,followed by high pressure, e.g., 1000 p.s.i. or more, for the remainderof the cure.

The B-stage material can be pulverized to form a powder, which can beshaped to form molded articles. If desired, reinforcing fibers, fillers,and pigments can be mixed in with the B-stage material.

If the faster catalysts, such as the alkali metal mercaptides, areemployed in the two-stage process, heating is not required in order toinitiate the formation of isocyanurate from isocyanate, althoughmoderate heat (e.g., 60 to 100 C.) is often employed in order to reducethe viscosity of the novolak-alkylene oxide condensate. Quenching to alow temperature (0 C., or below) is carried out shortly after thecatalyst has been added to the reaction mixture, for instance, fromone-half to 2 minutes after the initiation of the reaction. The B-stagematerial is then cured in a similar manner to that described above withrespect to the slower catalysts, except that lower temperatures (e.g.,as low as about 100 C.) may be employed.

The remarks above concerning the two-stage process apply when thereactants and catalyst are all mixed together at one time, as well aswhen the process is carried out by first forming anisocyanato-terminated prepolymer.

EXAMPLE 3 Preparation of fiber-reinforced composites (1) Preparation ofIsacyanate-Capped Prep0lymer. A novolak-propylene oxide condensate (xand n from Formula II were 5.7 and 2.4, respectively) (74.4 grams, 0.3equivalent of OH) that was warmed to 6080 C. to reduce its viscosity,was added to toluene diisocyanate (78 grams, 0.9 equivalent of NCO) atroom temperature. A slight exotherm was noted. The reaction mixture wascooled in a water bath and allowed to stand at room temperature forsixteen hours.

(2) Glass Fiber-Reinforced Composites.-Milled glass fiber (30 grams) and36 grams of the above-described prepolymer were blended in a Brabendermixer at room temperature until the mixture was uniform.Benzyldimethylamine (0.19 grams) and phenyl glycidyl ether (0.24 grams)were then added and the mixture was further mixed. The resulting uniformmixture was then compression molded under the same molding conditionsdescribed above in Example 2 to yield fiber glass reinforced plaqueswhich were removed from the mold without cooling.

(3) Sisal-Reinforced C0mposites.-In a similar manner, a composite wasprepared from 38 grams of the prepolymer and 30 grams of sisal.

(4) Asbestos-Reinforced Composites-Compression molded plaques wereprepared from 30 grams of prepolymer and 30 grams of asbestos in themanner described above.

EXAMPLE 4 Cast polyisocyanurates from novolak-propylene oxide condensateand isocyanates (1) A novolak-propylene oxide condensate (x was 5.7; nwas 4.5) (5.5 grams, 0.015 equivalent of OH) containing 0.2 milliliterof a 1M solution of lithium thiopheuoxide in dimethylformamide wasdegassed at 70 C. by evacuation at about mm. Hg. Toluene diisocyanate(2.94 grams, 0.02 equivalent of NCO) was then added by a syringedirectly into the reaction mixture, and the mixture was mixed with astirring rod. No flow was observed in less than one minute, and afterabout two minutes, a solid product was obtained shaped in a rodconforming to the shape of the reaction vessel.

(2) In a similar manner, a cast product was obtained from anovolak-propylene oxide condensate (x=5.7; 11:45) (5.5 grams, 0.015equivalent of OH), 0.2 milliliter of a 1M solution of lithiumthiopheuoxide, and bis(4-isocyanatophenyl)methane (3.75 grams, 0.03equivalent to NCO). No flow was observed at about less than one minute.

3) A novolak-propylene oxide condensate (10:5 .7, n-==4.5) (5.5 grams,0.015 equivalent of OH) containing 0.2 milliliter of a 1M solution oflithium thiophenoxide in dimethylformamide was degassed at 100 C. byevacuating at about 100 mm. Hg. A polymethylene polyphenyl isocyanate(2.94 grams, 0.02 equivalent of NCO) was added directly to the reactionmixture by a syringe. The mixture was mixed at 100 C. No flow wasobserved at less than two minutes, and after eight minutes, a castproduct was obtained in the shape of the reaction vessel.

The foregoing Examples 3 and 4 illustrate the process of the inventionwhen carried out as a one-stage processl When using the fast catalystssuch as alkali metal mercaptides, heating is not required, although itmay be employed as a means for reducing the viscosity of thenovolak-alkylene oxide condensate. When using the slower catalysts,heating to a moderately elevated temperature (e.g., 70 to 100 C.) isusually employed to initiate the reaction. In order to achieveessentially complete reaction with either fast or slow catalysts, apost-cure is often employed at elevated temperatures of, for example, upto 200 C. for a period of from about 5 to 30 minutes.

EXAMPLE 5 As a general rule, more flexible products are obtained withlonger polyoxyalkylene ether chains in the alkylene oxide-novolakcondensates and with lower isocyanate to hydroxyl ratios. Conversely,shorter polyether chains and higher NCO/OH ratios lead to harder, lessflexible products.

In order to illustrate the practical application of these principles, anumber of polyurethane-isocyanurate thermoset compositions were madefrom tolylene diisocyanate (TDI) and propylene oxide condensates of aphenol-formaldehyde novolak having an average of 5.7 phenol moieties permolecule (i.e., x in Formula 11 is 5.7). The condensates had varyingpolyether chain lengths, and

.11 varying NCO/OH ratios were used. The data are presented below inTable IV.

Sample Nos. (a) through (e) and (h) were prepared by the two-stageprocess using benzyldimethylamine and phenyl glycidyl ether catalyststhat was illustrated in Example 2. (In fact, Samples (c), (d), (e) and(h) are Sample Nos. 1, 2, 3 and 4, respectively, of Example 2.) SampleNos. (f), (g) and (i) through (k) were solution cast by a one-stageprocess. Sample No. (f) was solution cast onto glass from a 30-percentsolids solution in dioxane. 7 grams of condensate (0.025 equivalents ofOH) and 4.4 grams of T DI (0.05 equivalents of NCO) were employed. Thecatalyst was 0.25 milliliters (0.25 millimoles) of 1M solution oflithium p-chlorophenyl mercaptide in dioxane. The cast solution wasplaced in a 100 C. oven for 30 minutes to volatilize the solvent andcure the film. Sample (j) was produced in the same manner.

Sample (g) was also solution cast onto glass from a solution containing14 grams of condensate (0.05 equivalent of OH), 8.8 grams of TDI (0.1equivalent of NCO) and 0.1 gram of stannous di(octyl sulfide), i.e.,

The cure was the same as in Sample No. (f). Sample Nos. (i) and (k) wereproduced in the same manner as Sample (g).

TABLE IV Poly- Per- Penduether cent lum chain NOO/ Tensile Tensileelonimpact, length, H modulus, strength, ga- Tg, foot-lbs/ n ratiop.s.1. p.s.i. tion C. cubicinch What is claimed is:

1. A normally solid, fusible composition capable of being transformedinto a thermoset composition by subjecting said fusible composition toheat, wherein said fusible composition comprises the reaction product of(a) an alkylene oxide condensate of a novolak, (b) a stoichiometricexcess of an organic polyisocyanate, and (c) a catalytically effectivequantity of a catalyst for promoting the formation of isocyanurate fromisocyanate, where 12 in the reaction is interrupted by cooling beforereaching thermoset stage.

2. The normally solid, fusible composition of claim 1 wherein saidnovolak is a condensation product of phenol and formaldehyde.

3. The normally solid, fusible composition of claim 2 wherein saidalkylene oxide has from 2 to 4 carbon atoms.

4. Process which comprises the steps of (l) reacting (a) an alkyleneoxide condensate of a novolak, with (b) a stoichiometric excess of anorganic polyisocyanate, to form a composition containing urethane groupsand isocyanate groups, (2) contacting said composition with acatalytically effective amount of a catalyst for promoting the reactionof isocyanate to form isocyanurate groups, provided that step (2) iscarried out for a period of time insufficient to produce a thermosetcomposition, (3) cooling the product of step (2) to a temperature lowenough to stop significant further reaction, to produce thereby anormally solid, fusible composition, and (4) subjecting said fusiblecomposition to heat in order to produce a thermoset compositioncontaining both urethane groups and isocyanurate groups.

5. Process which comprises the steps of 1) reacting (a) an alkyleneoxide condensate of a novolak, with (b) a stoichiometric excess of anorganic polyisocyanate, in the presence of (c) a catalytically effectiveamount of a catalyst for promoting the formation of isocyanurate groupsfrom isocyanate groups, provided that step (1) is carried out for aperiod of time insufficient to produce a thermoset composition, (2)cooling the product of step (1) to a temperature low enough to stopsignificant further reaction, to produce thereby a normally solid,fusible composition, and (3) subjecting said fusible composition to heatin order to produce a thermoset composition containing both urethanegroups and isocyanurate groups.

References Cited UNITED STATES PATENTS 3,745,133 7/1973 Comunale 2602.5AW

3,723,367 3/1973 Chow 260-2.5 AB

FOREIGN PATENTS 934,629 8/1963 Great Britain 260- AP DONALD E. CZAJ A,Primary Examiner C. W. IVY, Assistant Examiner US. Cl. X.R.

260-2.5 AP, 2.5 AW, 37 N, 38, 77.5 NC

1. A NORMALLY SOLID, FUSIBLE COMPOSITION CAPABLE OF BEING TRANSFORMEDINTO A THERMOSET COMPOSITON BY SUBJECTING SAID FUSIBLE COMPOSITION TOHEAT, WHEREIN SAID FUSIBLE COMPOSITION COMPRISES THE REACTION PRODUCT OF(A) AN ALKYLENE OXIDE CONDENSATE OF A NOVOLAK, (B) A STOICHIOMETRICEXCESS OF AN ORGANIC POLYISOCYANATE, AND (C) A CATALYTICALLY EFFECTIVEQUANTITY OF A CATALYST FOR PROMOTING THE FORMATION OF ISOCYANURATE FROMISOCYANATE, WHEREIN THE REACTION IS INTERRUPTED BY COOLING BEFOREREACHING THERMOSET STAGE.